Draught-proofing and keeping heat in the home

A building loses heat in two ways: through the structure itself – walls, windows and roof – and through air exchange. The second is often underestimated. Warm air rises and escapes through gaps higher up, while cold air flows in lower down. Wind also pushes air through cracks on the weather side. A large share of heat loss can come from this uncontrolled air exchange.

Sealing reduces this unplanned exchange. But it does not replace deliberate airing: people constantly release moisture into the room air when breathing, cooking, showering and drying laundry. It has to get out. If it stays, it condenses on the coldest spots – window frames, outside corners, behind cupboards – and mould can grow there.

Curtains, blinds and shutters work differently: they hold a still layer of air in front of the cold glass. Still air conducts heat poorly, which is exactly why it insulates – on the same principle as a down jacket.

The most important rule when sealing: vents, air bricks and air supply openings for stoves, fireplaces and gas appliances always stay clear. Many combustion appliances take their combustion air from the room. If that air runs short, the fuel burns incompletely and carbon monoxide forms – a gas you can neither see nor smell, which can kill. A stove can also push exhaust back into the room.

So before sealing, note all openings that belong to stoves or gas appliances or serve moisture control, and leave them alone. Rooms with stoves or gas appliances are only sealed more tightly after professional assessment. A carbon monoxide alarm gives extra safety.

If there is a draught at sockets or switches on outside walls, do not open them yourself to seal them – that is electrical work and belongs to a qualified electrician.

First, find the leaks. On a windy day, slowly move a damp hand or a light feather along window frames, doors, the letterbox and pipe openings. Where it feels cool or the feather flutters, there is a leak.

Draught strip comes in different thicknesses and shapes. It has to match the gap: too thin and it does not seal, too thick and the window will no longer close properly and the frame is strained. The surface must be clean and dry for the adhesive. Brush seals or a draught excluder help under doors, and a cover with a brush or flap helps at the letterbox.

Close curtains and blinds in the evening and open them in sunshine during the day so the warmth comes in. Radiators should stay uncovered – a curtain in front of one sends the heat behind the fabric to the window. Air the rooms briefly and thoroughly several times a day with the window wide open, instead of leaving it permanently tilted.

If the heating fails, sealing becomes even more important. Then you concentrate on one room that should stay warm – ideally small, with few outside walls and on the sunny side. Doors to unused rooms stay closed, and a blanket in front of the door keeps out further draughts.

Simple measures also help in the short term: film or bubble wrap on window panes, rugs or blankets on cold floors, curtains closed during the day too on windows without sun. Even in this situation, brief airing stays important, because humidity rises quickly in a small, crowded room.

Draught strip and draught excluders are small measures that do not alter the building fabric. In rented homes they are usually unproblematic; anything that changes the structure should be discussed with the landlord first. Insulating walls, roofs and facades is a separate subject: it changes how moisture moves through the building and therefore needs professional planning.

Seals age. They harden, tear or come loose. A quick check before each winter – feather or hand along the windows – shows where improvements are needed. That saves heating costs in everyday life and leaves you better prepared for an outage at the same time.